1. Field of the Invention
This invention relates to an electronic control device for an engine of an automobile or other type of vehicle, what is called an engine control unit (hereinafter referred to as an ECU), and more specifically to a control circuit module that forms the ECU and an intake air passage body to which the control circuit module is mounted.
2. Prior Art
(1) Japanese Patent Laid-open No. Sho 58-174145 discloses a technique in which the ECU is mounted on a side surface of an intake pipe. (2) Japanese Patent Laid-open No. Hei 9-508954 discloses a technique in which the ECU is mounted on an electronic control throttle body. (3) Japanese Patent Laid-open Nos. Hei 7-83132 and Hei 10-274111 disclose a technique in which the ECU is provided inside an air cleaner. Further, Japanese Patent Laid-open No. Hei 5-231899 discloses a technique in which heat generated from a bridge circuit and a control circuit including therein a detector element of an intake air flow rate measuring device is dissipated and transferred onto an intake air.
The arrangements of (1), (2), and (4) have a problem that heat generated from the ECU is not sufficiently dissipated. In the arrangement of (3), in which the ECU is provided inside the air cleaner and cooled by the intake air, ease of assembly is a major problem to be solved. In addition, since a circuit board size involved with the ECU is larger than the intake air flow rate measuring device, this presents another problem of an increased intake air resistance in an intake air passage when the ECU is provided inside the intake air passage.